[Sconrad]

Disclaimer: This is kind of a hack job solution and should only be tried if the previous suggestions did not work or you don't have time to try them. Also, although this fix worked for us, I can't say I did a ton of research into how exactly it worked so I can't guarantee it will work (Mr. McKaskle probably could better explain exactly why this works, etc.).

Our team encountered this early on in the build season. Drive -> SetSafetyMode vi (I'm not sure if that's the exact name, I don't have LabVIEW up in front of me) has a boolean input labeled something like Enabled? By placing this vi in the Begin vi in between the Open and setRefNum vis, we managed to make the error go away. Again, we only made the error go away, not the problem itself. The above suggested solutions are probably better ideas in general if you have the time to execute them.